Nondestructive Methods for Recovery of Biological Material from Human Teeth for DNA Extraction

From Jane Doe to Sofia: DNA Extraction Protocol from Bones and Teeth without Liquid Nitrogen for Identifying Skeletal Remains

DNA analysis plays a crucial role in forensic investigations, helping in criminal cases, missing persons inquiries, and archaeological research. This study focuses on the DNA concentration in different skeletal elements to improve human identification efforts. Ten cases of unidentified skeletal remains brought to the Institute of Forensic Medicine in Timisoara, Romania, underwent DNA analysis between 2019 and 2023. The results showed that teeth are the best source for DNA extraction as they contain the highest concentration of genetic material, at 3.68 ng/µL, compared to the petrous temporal bone (0.936 ng/µL) and femur bone (0.633 ng/µL). These findings highlight the significance of teeth in forensic contexts due to their abundant genetic material. Combining anthropological examination with DNA analysis enhances the understanding and precision of identifying human skeletal remains, thus advancing forensic science. Selecting specific skeletal elements, such as the cochlea or teeth, emerges as crucial for reliable genetic analyses, emphasizing the importance of careful consideration in forensic identification procedures. Our study concludes that automated DNA extraction protocols without liquid nitrogen represent a significant advancement in DNA extraction technology, providing a faster, more efficient, and less labor-intensive method for extracting high-quality DNA from damaged bone and tooth samples.

Forensic DNA extraction methods for human hard tissue: A systematic literature review and meta-analysis of technologies and sample type

DNA identification of human remains has a valuable role in the field of forensic science and wider. Although DNA is vital in identification of unknown human remains, post-mortem environmental factors can lead to poor molecular preservation. In this respect, focus has been placed on DNA extraction methodologies for hard tissue samples, as these are the longest surviving. Despite decades of research being conducted on DNA extraction methods for bone and teeth, little consensus has been reached as to the best performing. Therefore, the aim of this study was to conduct a thorough systematic literature review to identify potential DNA extraction technique(s) which perform optimally for forensic DNA profiling from hard tissue samples. PRISMA guidelines were used, by which a search strategy was developed. This included identifying databases and discipline specific journals, keywords, and exclusion and inclusion criteria. In total, 175 articles were identified that detailed over 50 different DNA extraction methodologies. Results of the meta-analysis conducted on 41 articles - meeting further inclusion criteria - showed that statistically significant higher DNA profiling success was associated with solid-phase magnetic bead/resin methods. In addition, incorporating a demineralisation pre-step resulted in significantly higher profiling successes. For hard tissue type, bone outperformed teeth, and even though dense cortical femur samples were more frequently used across the studies, profiling success was comparable, and in some cases, higher in cancellous bone samples. Notably, incomplete data sharing resulted in many studies being excluded, thus an emphasis for minimum reporting standards is made. In conclusion, this study identifies strategies that may improve success rates of forensic DNA profiling from hard tissue samples. Finally, continued improvements to current methods can ensure faster times to resolution and restoring the identity of those who died in obscurity.

Dental Radiographic/Digital Radiography Technology along with Biological Agents in Human Identification

The heavy casualties associated with mass disasters necessitate substantial resources to be managed. The unexpectedly violent nature of such occurrences usually remains a problematic amount of victims that urgently require to be identified by a reliable and economical method. Conventional identification methods are inefficient in many cases such as plane crashes and fire accidents that have damaged the macrobiometric features such as fingerprints or faces. An appropriate recognition method for such cases should use features more resistant to destruction. Forensic dentistry provides the most appropriate available method for the successful identification of victims using careful techniques and precise data interpretation. Since bones and teeth are the most persistent parts of the demolished bodies in sudden mass disasters, scanning and radiographs are unrepeatable parts of forensic dentistry. Forensic dentistry as a scientific method of human remain identification has been considerably referred to be efficient in disasters. Forensic dentistry can be used for either "sex and age estimation," "Medical biotechnology techniques," or "identification with dental records," etc. The present review is aimed at discussing the development and implementation of forensic dentistry methods for human identification. For this object, the literature from the last decade has been searched for the innovations in forensic dentistry for human identification based on the PubMed database.

Effect of postmortem interval and conditions of teeth on STR based DNA profiling from unidentified dead bodies

Teeth are important exhibits to establish the identity of unidentified dead bodies by DNA profiling. Tooth acts as a cage to protect DNA from harsh environmental conditions. Unidentified bodies are sometimes found many years after death causing loss of valuable soft tissues which can be used for DNA extraction. Skeletal remains and dental evidence provide the best alternative when decomposed or burnt bodies are examined to establish the identity. In this study, the powder-free method was used to extract DNA from ninety-five teeth of unidentified dead bodies across seven years (2014-2020). Intact and broken dental remains were analyzed majorly from decomposed remains. The present study reports successful STR profiles obtained from dental evidence using powder free method. Complete DNA profiles were obtained from intact teeth while damaged teeth either gave partial profiles or no results. This data suggest that intact teeth are excellent samples for DNA profiling from decomposed unidentified dead bodies even with greater post mortem interval. Findings from this study can hence be useful in establishing the identity in forensic and archeological casework.

Assessing the viability of carious lesions in human identification using STR typing

Human teeth have become a prominent source of DNA for human forensic identification as their biological structure is highly resistant to extreme conditions. Previous forensic identification was mainly dependent on the pulp and the other hard tissues of intact teeth. However, there is high likelihood that only carious teeth can be available for forensic analysis. This study aimed to validate the use of the carious part of the teeth for forensic identification and to compare two DNA extraction methods-the operative technique with the cervical cut technique for human identification using STR typing. The reliability of STR markers in carious part of the teeth was evaluated in 120 carious teeth (60 dental pulp and 60 dentinal carious tissues, respectively) with considerable coverage of gender type and age range to avoid false exclusions. The study was performed on genuine data set where samples have been extracted by proficient dentist during the treatment operation and collected for further analysis. Complete DNA was extracted and the corresponding human identification profile was obtained using the GoldenEye™DNA ID system 20A kit. The operative technique showed a conservative approach to the sampling of carious tissues and allowed safe access to collect carious tissues, whereas the cervical cut technique permitted access to the root canals and complete sampling of the pulp tissues. The findings indicated that there was no significant association between the cervical cut and operative cut techniques (p = 0.165). In addition, there was no statistically significant association between the various teeth types and the obtained profiles observed. The operative technique, by drilling holes on the defected surface of carious human teeth and gentle hand excavation of carious tissues, was indicated to be very efficient, preserving, time-saving, and cost-effective in the recovery of human DNA from carious teeth. The result gives new insights that the carious tissues of human carious teeth might be as valid as the healthy teeth for forensic human identification.

Fragment analysis in forensic anthropology

Anthropological analysis of fragmentary evidence can be challenging but diverse methods allow substantial information to be gleaned. Scanning electron microscopy/energy dispersive X-ray spectroscopy enables determination if bone and/or tooth tissue is present. Protein radioimmunoassay or DNA analysis can establish the species present. Histological analysis can assist in species determination and reveal information about thermal changes. Radiocarbon analysis with special reference to the modern bomb-curve can clarify the postmortem interval. Anthropologists should also be aware that DNA analysis not only can enable positive identification but assist in the evaluation of sex and age at death.

DNA recovery and analysis from skeletal material in modern forensic contexts

The generation of a DNA profile from skeletal remains is an important part of the identification process in both mass disaster and unidentified person cases. Since bones and teeth are often the only biological materials remaining after exposure to environmental conditions, intense heat, certain traumatic events and in cases where a significant amount of time has passed since the death of the individual, the ability to purify large quantities of informative DNA from these hard tissues would be beneficial. Since sampling the hard tissues for genetic analysis is a destructive process, it is important to understand those environmental and intrinsic factors that contribute to DNA preservation. This will serve as a brief introduction to these topics, since skeletal sampling strategies and molecular taphonomy have been discussed in depth elsewhere. Additionally advances in skeletal DNA extraction and analysis will be discussed. Currently there is great variation in the DNA isolation methods used by laboratories to purify DNA from the hard tissues; however, a standardized set of short tandem repeat (STR) loci is analyzed by many US laboratories to allow for comparisons across samples and jurisdictions. Recent advances have allowed for the generation of DNA profiles from smaller quantities of template DNA and have expanded the number of loci analyzed for greater discriminatory power and predictions regarding the geographic ancestry and phenotype of the individual. Finally, utilizing databases and expanding the number of comparison samples will be discussed in light of their role in the identification process.

Sources of Materials for Paleomicrobiology

The Paleomicrobiology establishes the diagnosis of ancient infectious diseases by studying ancient pathogens. This recent science also analyzes the evolution of these pathogens, virulence, and their adaptation to their habitat and their vectors. The DNA persists a long time after the death of an organism despite the chemical and enzymatic degradation. The possibility of sequencing bacterial, viral, parasitic and archaeal DNA molecules persists over time.Various sources are used for these studies: frozen tissue and particularly human tissue are a exceptional source for the analysis because at very low temperatures, all biological activity is suspended. The coprolites are a source of choice for studying the human microbiome. Other sources, the ancient bones are the most abundant, however, they may contain only small amounts of DNA due to natural leaching. When the use of the tooth is possible, is a particularly interesting source because of its highly mineralized structure, which gives greater persistence than bone. The calcified tartar deposited on teeth is a source of interest for the study of oral microbiome.All these sources are subject to precautions (gloves and masks hat) at the time of sampling to avoid cross contamination and also be listed in the most precise way because they are precious and rare.